Switching to the Temporal Location

Top surgeons explain why they prefer temporal clear corneal incisions, and how you can incorporate this technique into your OR.

May 1, 2000

As you know, the clear corneal procedure is
now the choice of many cataract surgeons. Last month, we looked at ways to
incorporate it into your surgical routine, and how to improve your technique.

Here, we'll take a closer look at one aspect
of this cataract surgery choice -- the temporal clear corneal incision. We
asked leading surgeons to tell us why (and when) they choose the temporal
location, to share their temporal incision approaches, and to offer some
strategies for adjusting your OR procedure.

Location, location, location

After I. Howard Fine, M.D., presented his
clear corneal incision to the American Society of Cataract and Refractive
Surgery in 1992 (emphasizing the temporal location), it became apparent to many
surgeons that the temporal location provided the most advantages.

Shortly thereafter, Charles H. Williamson,
M.D., of Baton Rogue, La., became the first surgeon to perform temporal clear
cornea using topical anesthesia. He offered the first seminar for surgeons
touting the temporal location in August 1992.

"There are several reasons for doing
the surgery temporally," Dr. Williamson says. "When the patient is
undergoing surgery under topical anesthesia, they're asked to fixate on the
microscope light. If you're temporal, the patient can look directly at the
light. If you're doing it superiorly, the patient has to look down, and there's
nothing to fixate on."

�Temporally, you have
better exposure to the surgical limbus, even in deep-set eyes.

�In 1992 incisions were
a little
larger. Dr. Williamson says it was his belief that because the incision was
essentially perpendicular to the direction of lid blink, there would be less
wound gaping and leaking.

�The end of Bowman's
membrane is elliptical, meaning that the temporal cornea is farther from the
visual axis. As a result, any surgically-induced astigmatism caused by the
surgery will be minimized.

Harry Grabow, M.D., started superiorly with
clear cornea in 1992, but switched to temporal for several reasons.

"Originally I started with a 3.2 mm
phaco and foldable incision, but after fewer than 20 cases I discovered that I
could induce as much as three diopters of against-the-rule astigmatism with
that incision," Dr. Grabow says. "Later on, when I did cell counts on
those patients, I found a central corneal cell loss of around 14% in some
cases.

"I quickly moved to the temporal
location, and I found that the induction of astigmatism was half that induced
at the superior location. The loss of endothelial cells was also half that of
the superior location."

Clear corneal pioneer Dr. Fine agrees.
"The temporal location is the furthest distance from the visual axis on
the cornea. The central axis is nasally placed. As a result, the flattening
that occurs at the incision site is less likely to be transmitted to the visual
axis from the temporal location than from any other.

"The temporal location also provides
much easier access to the temporal periphery than any other area in the
cornea," he continues, "and that's because the angle of the lid sits
beneath it. So in deep-set eyes or prominent brows we don't have to use bridal
sutures, and we don't have to turn the eye down. We don't have to cut or touch
a needle through the conjunctiva.

"In addition, it's much easier to move
instruments in and out of the eye."

Dr. Fine adds that along with the temporal
location being the most astigmatically-neutral and ergonomically easiet for the
surgeon, there's an even bigger benefit. "The location of the lateral
canthal angle lets the eye drain naturally," he says. "That's the
greatest advantage. With other incisions, fluids can pool in the conjunctiva.
With the temporal incisions, fluids drain away -- there's no pooling."

Incision shape and plane

When Dr. Fine introduced clear cornea, most
cataract incisions were larger. With the introduction of injectable intraocular
lenses (IOLs), surgeons were able to make much smaller incisions. Today, there
are three prominent temporal clear corneal approaches.

"We learned from the studies of Paul
Ernest and others, the closer we can make the clear corneal incision to a
square in dimension, the stronger the incision will be postoperatively,"
Dr. Grabow explains. "However, most surgeons make a self-sealing incision
that's physiologically stable.

"I prefer to make a trapezoid incision
that has a smaller internal opening and a larger external opening. That type
was originally designed by Dr. Williamson. It gives me a safer internal valve
for sealing the incision and allows increased maneuverability of the
instruments.

"The incision can be made as a
single-plane or as a two-plane incision. The two-plane incision involves a
vertical groove incision that's parallel to the limbus and extends slightly
beyond the margins of the second-plane incision, which will enter the anterior
chamber. The depth of that groove can be 300, 400, or 600 microns.

"The 600 micron depth was recommended
by David Langerman for separation of compression forces postopera-
tively," he adds. The Langerman hinge incision was designed to be more
resistant to eye rubbing.

"In 80% to 90% of cases, I use a
single-plane incision," Dr. Grabow continues. "This is because I
don't intend to use that incision to alter astigmatism.

"If the patient has against-the-rule
astigmatism, I'll make a limbal relaxing incision (LRI) of 550 microns for the
appropriate arc length, and possibly couple it with an additional LRI or
astigmatic keratotomy (AK) at the opposite meridian. I'll use the proximal LRI
as the vertical groove component of the two-plane phaco incision.

"At the conclusion of all cases I
hydrate the stroma with balanced salt solution."

Using a groove

Surgeons may choose different approaches for
different patients, but they usually favor one type. Dr. Williamson prefers to
use the groove, or step, incision.

"People talked about the two-step
incision, or groove incision, and said the incisions were stronger. We started
making a hinge for the same reason," he says. "We found that once the
wounds got below 3 mm, it didn't really matter which of the three incision
types you made: a single, a grooved incision (or a step), or the hinge. The
wounds didn't leak."

With that said, Dr. Williamson explains why
he still favors the step.

"The real reason to make a step
incision is that the beveled incision made the corneal edge of the incision so
thin it would sometimes fray and cause a problem. That thin little edge would
get chewed up. So what I did by making this incision or groove into the cornea
was make the edge much thicker. That was my reason for making the groove -- not
to reduce wound leakage.

"I also think it's the easiest incision
to learn. The doctor can make a groove and then make the tunnel incision."

Dr. Williamson explains his technique:
"I make a 2.5 mm groove into the clear cornea just ahead of the
conjunctiva. I use a Diamatrix step knife with a guarded blade to make a groove
300 to 400 microns deep. I then extend the blade and do a side stab incision to
the left, because I'm right-handed. I inject a viscoelastic through the
side-step incision and fill the anterior chamber, replacing the aqueous as I
inject. I use a 2.5 to 2.9 mm Diamatrix trap blade diamond to create a
trapezoidal corneal tunnel about 1.75 mm in length."

"I use a Rhein diamond keratome that
has a step advancement. First I make a 300 micron-deep groove. Then I advance
the blade fully, and use it to make a 2.8 mm clear corneal tunnel, with a
length of 1.75 mm before it enters the anterior chamber," Dr. Steinert
says.

"The reason for the groove is that it
gives strength to the external corners of the incision. Especially for
beginning surgeons, this step helps avoid tearing of the external corners
during surgical maneuvers that stress the incision," Dr. Steinert explains.
"In some cases, I also use a single-plane incision. I get the same wound
integrity either way."

�Insure strong
incisions. Do a groove to ensure
that the external corners of the incision are stronger.

�Finish as phaco. If you can't complete the case as phaco and you have
to convert to extracapsular cataract extraction, go to a superior site and make
a conventional corneoscleral incision. Otherwise, high astigmatism is likely
from the wide corneal wound.

�Be comfortable. The enhanced visualization and maneuverability from
temporal incisions is vastly superior to going over the brow for superior
incisions. Once you adapt, you'll love it!
The biggest obstacle is being comfortable during the surgery. A few surgeons
sit superiorly and use instruments both nasally and temporally, which Dr.
Steinert says doesn't work well for his technique. He has a Stryker OR bed that
lets him sit to the side and allows good access for his legs.
If necessary, you can adjust the patient's position. This usually means moving
the patient superiorly and/or toward you. The oculars of the microscope may
need to be tilted to full horizontal. If you're short, you can tilt the whole
microscope as well to create adequate comfort.

�The opposite eye. When operating on the eye that is opposite your
dominant hand, the incision can be skewed superotemporally. But don't do a
clear cornea incision between 11 and 1 o'clock, because the induced astigmatism
may be considerable. Astigmatism shifts are minimal from incisions made between
8 and 10 o'clock.

When you move to the temporal location, it's
also important to make sure you can fit your legs under the table and still
reach the microscope pedal and phaco machine pedal, Dr. Grabow says. He found
it helpful to change the objective lens on the microscope to a shorter working
distance, so that he could raise the table a little higher to allow more room
for his legs.

Dr. Grabow also suggests that you tilt the
patient's head slightly toward you and angle the microscope body tube slightly
toward you. This keeps the microscope's body tube perpendicular to the plane of
the iris, while allowing you to sit up straight.

"The surgeon will also notice that he
can no longer rest his hands on his patient's forehead for stability," Dr.
Grabow says. "I recommend gentle placement of the hands on the temporal
area. Excessive pressure will cause the head to rotate away from the surgeon, a
phenomenon prevented by taping the head to the table."

Dr. Grabow adds that it's important to
remember that your hands will be held more closely together for temporal
surgery than they usually are during superior surgery.

Finding your spot

All the surgeons who've outlined the merits
of the temporal clear corneal incision above agree that it may take you some
time to adapt to working from the different location. But they also agree that
after the transition, this approach will become ergonomically easier than other
approaches.

Considering the benefits both you and your
patients will reap, this is definitely an incision worth trying.

When the Temporal Location Isn't Appropriate

While a temporal clear cornea incision is
the right location for many cataract patients, in some cases, you may need to
look elsewhere.

Roger F. Steinert, M.D., says he chooses
another location:

�when a patient has
peripheral degeneration of the cornea

�when enlargement of
the incision is needed (such as when inserting a non-
foldable IOL)

�when a combined
glaucoma procedure is planned.

Charles H. Williamson, M.D., adds that
when you want to induce astigmatism you should use a different approach. Also,
for peripheral corneal disease such as corneal melt, a scleral incision is more
appropriate.

What About Refractive Surgery Patients?

How does refractive surgery affect your
temporal location preference? Some surgeons say it shouldn't, while others
recommend some precautionary measures to take so that laser-assisted in situ
keratomileusis (LASIK), photorefractive keratectomy (PRK) or radial keratotomy
(RK) patients don't become hyperopic after cataract surgery.

"It's important to note that with RK
you have to modify the current IOL calculations, and you have to have a corneal
topographer to calculate the true keratometric reading, rather than using a
manual keratometer," says Charles H. Williamson, M.D. "Otherwise your
result will be too hyperopic."

"I would consider using a superior
scleral pocket incision in eyes that have had corneal refractive surgery such
as LASIK or RK," says Harry Grabow, M.D. "I know there are some
surgeons who've been successful with temporal clear corneal incisions in eyes
that have had RK. However, there have also been cases reported where a temporal
clear corneal incision was used in an eye with previous RK in which the RK
incisions split open and required significant suturing in order to stabilize
the cornea."

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Now more than ever before, ophthalmologists are required to think as an MD and a CEO. The right balance of clinical and practice management skills is critical for a practice to flourish. Each month only one publication delivers the essential strategies needed to navigate and grow today’s ophthalmology practice. Led by Chief Medical Editor Larry Patterson, MD, Ophthalmology Management provides all the tools ophthalmologists need to succeed, bringing them the latest practice management pearls, clinical advancements and medical economics they need to help their practices grow.